This invention is generally in the area of enzymes and especially temperature stable enzymes.
Acid proteases are a well established group of proteolytic enzymes which digest proteins and peptides in an acidic solution. Some well known acid proteases are pepsin, gastricsin, chymosin, and cathepsin D. Most of these enzymes share similar amino acid sequences, three-dimensional structures, active-site structures, and catalytic mechanisms. See J. Tang, Acid Proteases, Structure, Function, and Biology, (Plenum Press, New York, 1977); V. Kostka, Aspartic Proteases and Their Inhibitors, (Walter de Gruyter, Berlin, 1985); and Tang and Wong, J. Cell. Biochem., 33, 53-63 (1987), for a general review of acid proteases. A common property of the active site structures of acid proteases is that these enzymes are inhibited by pepstatin, a transition-state analogue inhibitor, as discussed by Marciniszyn, et al., J. Biol. Chem., 251, 7088-7094 (1976). Because these proteases contain two aspartic acid residues in their catalytic sites, they are also called aspartic proteases. The structure and function relationships of aspartic proteases is a topic of current research interests because some aspartic proteases are involved in diseases, such as renin hypertension and acquired immunodeficiency disease (an acid protease is associated with the maturation of the Human Immunodeficiency Virus), and the availability of high-resolution crystal structures of several aspartic proteases has made these enzymes attractive models for the study of structure-function relationships.
It is therefore an object of the present invention to provide a unique acid protease.
It is another object of the present invention to provide an acid protease having exceptional stability at high temperatures and low pH.
It is a still further object of the present invention to provide methods for use of a thermostable, acid stable acid protease.